Twelve people died after torrential rains flooded a subway in the central Chinese city of Zhengzhou, as shocking images showed passengers struggling against chest-high water inside a train carriage, AFP reports.

As dams burst and river embankments were breached in record downpours across Henan province, President Xi Jinping described the situation as "extremely severe" with flood control measures entering a "critical stage," state media reported Wednesday morning.

Around 200,000 city residents were evacuated, local government officials said, with soldiers leading rescue efforts in the city of over 10 million people, where days of rain have inundated the streets and subway.

Rainstorms submerged Zhengzhou's metro, killing 12 people and injuring five, while hundreds were rescued from the subway, city officials said in a Weibo post.

Nerve-shredding images shared on social media showed shocked passengers contending with the fast-rising waters inside a train carriage.

Rescuers cut open the roof of the coach to pull people to safety, local media reported. Others showed dramatic rescues of pedestrians in Zhengzhou from torrents gushing through the streets.

Relatives outside the city made anxious pleas on China's Weibo for information as communications to the city went down.

"Is the second floor in danger? My parents live there, but I can't get through to them on the phone," one user wrote. "I don't know more about their situation. I'm in Tianjin and my parents are in Zhengzhou," she said, giving her surname only as Hou when contacted by AFP. "I'm very anxious."-Photo: Sky News

(Video) 12 die in flooded Zhengzhou subway